Heat exchange screw conveyer



Sept. 9, 1952 c. A. RIETZ HEAT EXCHANGE SCREW CONVEYER 2 SHEETS SHEET 1 Filed Oct. 22, 1946 FIE-Ei 1 INVENTOR. Cr/ 14. Ens-f3 BY Ax/Z 1/ ATTORNEY Sept. 9, 1952 c. A, mm 2,610,033

HEAT EXCHANGE SCREW CONVEYER Filed Oct. 22, 1946 v 2 SHEETS-SHEET 2 INVENTOR (IQ/"7 14, E67;

"@QWM flTTORA/EY Patented Sept. 9, 1 952 HEAT EXCHANGE SCREW CONVEYER V Carl A. Rietz, San Francisco, Calif., assignor to Rietz Manufacturing 00., San Francisco, Calif., a corporation of California Application October 22, 1946, Serial No. 7c4,s91

This invention relates generally to material handling and treatment apparatus, particularly apparatus of the type making use of heat transfer screws having helicoidal flights for engaging the material.

1 It is an object of the invention to provide improved apparatus of the above character having an improved type of rotary screw characterized particularly by the use of a novel flight construction. i

A further object of the invention is to pro vide apparatus of the above character having a heat transfer screw particularly eiiective in promoting intermixing of the material being treated.

A further object of the invention is to provide an improved form of cooker for the treatment of various pulps or slurries, and which is characterizedby eflicient and rapid transfer of heat to the material being treated without injury to the same.

Another object of the invention is to'provide novel methods for the treatment of material by use of the foregoing apparatus, and applicable particularly where it is desired to secure an efficient exchange of heat with respect to the material. p i 1 Additional objects of the invention will appear from the following description in which the preferred. embodiments have been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure l is a side elevational view illustrating one embodiment of the invention.

Figure 2 is a detail showing a portion of the heat transfer screw.

Figure 3 is an enlargedcross-sectional detail showing the construction of the screw flight.

Figure 4 is a detail showing a modified form of screw using a mixing ribbon.

Figure 5 is a cross-sectional view taken laterally through Figure 4.

Figure 6 is a side elevation in section showing another embodiment in whichtwo screws are employed.

Figure 7 is a cross-sectional view taken along the line l''l of Figure 6.

That form of the invention illustrated in Figures 1 to 3 inclusive comprises an enclosing housing it provided with a feed hopper H, and a discharge conduit l2. Extending longitudinally within this housing there is a screw l3 adapted to be rotated from some suitable source of power. The screw is formed to receive heat transfer fluid, and utilizes the novel construction illustrated in Figures 1 to 3. Thus the screw n- 3 Claims. (01. 257-101) cludes the tubular shaft l4 which carries a helicoidally formed flight structure designated generally at It. cated construction and includes the metal walls ll, [8 and I9. Wall I! is disposed helicoidally about the shaft and has its inner edge attached to the same by welding 2 l. Wall 18 is preferably of lesserwidth than wall El, andis disposed in spaced substantially parallel relationship thereto. The inner edge of wall [8 is likewise attached to the shaft 14 by welding 22. Wall I9 is attachedto the walls I l and 18 substantially as illustrated in Figure 3. Thus as illustrated its one edge abuts the rear side oi-wall l? and is attached thereto by welding 23, and its other edge caps the outer periphery of wall If) and is attached thereto by weld connection 24.

In operation the screw is rotated in such adirection that the outer or exposedface of wall I! contacts and applies thrust to the material being handled. It will be not'edthat weld connection 23 lies completely behind the exposed face of wall I l', and therefore it is protected The space 26 within a the flight is adapted to receive a heat transfer against abrasion and wear.

fluid, and is in freecommunication at a'number of points with the interior of the shaft I 4,

as for example by means of one or more slots 21 and openings 28. Where the screw is being constructed in such amanner as to Withstand con siderable internal pressure, it is desirable to attach walls ii and [8 together at spaced points 'by means of the stay bolts or rivets 29.

At one end of the housing asuitable stuifing box or gland 3| is provided, by means of which steam or like heat transfer fluid supplied by way of pipe 32 is introduced into the passage through shaft M, and thusinto theflight. At-the other end of the housing a similar gland 33 is provided by means of which condensate is removed through pipe 3 3. i l i It will be evident that the apparatus described above can be used for a variety ofmaterial handling and treating operations. Assuming that it is desired to heat pulps or slurries such as are frequently found in the food industry, as for example sou or meat stocks; steam at a suitable pressure andtemperature is continuously supplied to the screw by way of pipe 32, and the material to be treatedis supplied through hopper. H either continuously or inter mittently. Rotation of the screw is in such a direction that there is a progression of the material toward the outlet end of the housing. The exposed face of the wall I1 is the only surface of The flight structure is of -fabri-- the flight which directly contacts and presses against the material being handled, and therefore the weld connections 23 and 24 are not weakened by abrasion. The fabricated flight construction provides a relatively high degree of strength to apply the desired thrust to the material and also to withstand internal pressure which may be applied. There is relatively good heat transfer from the steam introduced into the flight and the material being treated, whereby the material can be heated to any desired temperature before its discharge.

Figure 4 illustrates a modification of the structure shown in Figures 1 to 3 inc1usive. Thus in this instance the feed screw is provided with one or more so-called mixing ribbons 36. In this instance two such ribbons are provided and they are disposed 180 apart. Each ribbon consists of V a strap of metal formed helicoidally and having its inner edge attached at spaced points to the periphery of the flight I6. It will be noted that the pitch of each of the ribbons is the same, and that this pitch is substantially greater than the pitch of the flight [6. In Figure 4 the helicoid of the flight and of the mixing ribbons are in opposite directions, although as will be presently explained in some instance it is desirable that they be in the same direction. The ends of the ribbons are preferably-provided with inwardly extending vanes or paddles 31.

Assuming use of the screw illustrated in Figure 4 in a housing and associated parts substantially as illustrated in Figure 1, the mixing ribbons impart considerable turbulence to the material being treated as the screw rotates. lence materially aids in intermixing the material being treated, and in insuring relatively high heat transfer through the walls of the flight. This i by virtue of the fact that turbulence extends into the regions between convolutions of the flight, thus enabling a relatively high rate of heat transfer without undue localized heating of the material being treated. The vanes or paddles 31 sweep the ends of the housing, thus tending to prevent formation of pockets where material'may remain without entering into progressive treatment.

Figures 6 and '7 illustrate an equipment incorporating the present invention and particularly adapted for the heat treatment of various pulps or slurries, as, for example the pasteurization or cooking of food slurries like meat stocks. The apparatus consists of a suitable housing iii carriedbythe end standards 42, and within which are disposed the two screws 43a, 6319. These screws can be constructed substantially like the screw of Figure 4, although it is desirable that the helix of the flight and of the mixing ribbons be in the same direction. The walls of the housing 41 include the substantially semi-cylindrical wall portions 44 which underlie the screws, and which join along the central longitudinal rib it. The walls are provided with a suitable jacket d"! whereby heat transfer fluid such as steam may be applied to the-outerwalls of the housing. Connections can be made to this jacket .by pipes 48. Centrally of the housing there is a valve controlled pipe 49 through which the treated material can be discharged. Bysuitable' means such as gearing 5| the shafts of the two screwsare interconnected for synchronous rotation ,in oppositedirections. Packingglands 52 and .53 are provided at the ends .of the housing andconnect with pipes 54 and 55, for introduction of steam and removal of condensate.

To utilize the apparatus of Figure 6 a quantity Such turbu- 4 of material to be treated, such as soup or meat stock, is introduced into the housing with the two screws being driven in opposite directions. Steam is supplied to both of the screws whereby heat transfer occurs to the material being handled through the walls of the flights. At the same time steam or like heating fluid can be applied to the outer jacket 41. The screws are completely or substantially submerged by the batch of pulp being treated, and as the screws rotate the flights tend to urge the material in their vicinities longitudinally of the housing and in opposite directions toward the ends of the same. At the same time the mixing ribbons cause general turbulence and intermixing of the material to promote heat transfer as previously described. At the ends of the housing there is a general crossing over of the material, or in other words there is a general transfer of the material from the region of one screw to the other. Thus during its treatment within the housing the material generally progresses longitudinally of the housing in opposite directions in the regions of the two screws, with a cros over at the ends of the housing, and at the same time there is a Sidewise turbulent action or'sidewise regurgitation caused by the mixing ribbons.

I claim:

1. A heat transfersorew comprising a tubular shaft and a helicoidal flight carried by the shaft, said flight comprising a wall formed helicoidal and having its inner edge attached to the tubular shaft by a weld connection, the outer edge of 7 said wall forming the periphery of the screw, one face of said wall serving to engage and press against the material being handled, and two additional walls attached to the other face of said first named wall, one of said additional walls being helicoidal and being in equidistant spaced relationship with said first named wall With its inner periphery attached to said shaft by a Weld connection, the outer edge of said last named wall being formed to ya diameter substantially less than the diameter of the first named Wall, a third Wall in the form of a continuous band attached by weld connections to the first two mentioned walls and extending between the outer edge of the second named wall and that face of the first named wall which is oppositeto the face which engages and presses upon the material, and stay members extending between said'first two walls intermediate their inner and outer edges, all of said walls serving to definea closed space for receiving a heat transfer fluid, said Walls when viewed in section on a section plane coincident with the axis of the shaft being-disposed whereby the first and second walls are parallel, and the third wall is at right angles to the first and second Walls and has itsouter surface coincident with a cylinder.

2. A heat transfer screw comprising a tubular shaft and a helicoidal flightcarried by theshaft, said flight comprising a wall formed helicoidal and having its inner edge attached to thetubular shaft by a weld connection, the outer edge of said wall forming the periphery of the screw, one face of said wall serving to engage and press against the material being handled, and two additional .Walls disposed on the other face of said first named wall, one of said additional walls beinghelicoidal and being in'equidistant spaced relationship with said first named wall with its inner periphery attached by a weld connection to said shaft, and the third wall being in the form of a continuous band and having its one margin overlapping and welded to the outer peripheral edge of the second wall and having its other edge abutting and welded to that face of the first named wall which is opposite to the face which engages and presses upon the material, all of said walls serving to define a closed space for receiving a heat transfer fluid, said walls when viewed in section on a section plane coincident with the axis of the shaft being disposed whereby the first and second walls are parallel and the third wall is at right angles to the first and second walls and has its outer surface coincident with a cylinder which is smaller in diameter than the diameter of the first wall.

3. A heat transfer screw comprising a tubular shaft and a helicoidal flight carried by the shaft, said flight comprising a metal wall formed helicoidal and having its inner edge attached to the tubular shaft by a wall connection, the outer edge of said wall forming the periphery of the screw, one face of said wall servingto engage and press against the material being handled, and two additional metal walls disposed on the other side of said first named Wall, one of said additional walls being helicoidal and being in equidistant spaced relationship with said first named wall with its inner periphery attached by a weld connection to said shaft, and the third wall being in the form of a continuous band and having its one margin overlapping and welded to the outer peripheral edge of the second wall and having its other edge abutting and welded to that face of the first named wall which is opposite to the face which engages and presses upon the material, all of said walls serving to define a closed space for receiving a heat transfer fluid, said walls when viewed in section on a plane coin- 6 cident with the axis of the shaft being disposed whereby the first and second walls are substantially parallel and the third wall is at right antiles to the first and second walls and has its outer surface coincident with a cylinder which is smaller in diameter than the diameter of the first wall, and metal stay members attached to and extending between said first two walls intermediate their inner and outer edges.

CARL A. RIETZ.

REFERENCES CITED The following references are of record in the file of this patent:

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